预烧温度对LiZn铁氧体微结构和性能的影响

研究了预烧温度对LiZn铁氧体微结构、密度、气孔率和磁性能的影响.结果表明,预烧温度影响粉体的活性,适宜的预烧温度是获得良好显微结构和高性能铁氧体的必要保证.气孔率P减小,饱和磁感应强度Bs、矩形比Br/Bs(Br为剩余磁化强度)增加;平均晶粒尺寸Dm增大,矫顽力Hc减小.P和Dm决定铁磁共振线宽ΔH的大小,但前者的作用比后者大.当预烧温度为800 ℃时,材料的P 最小,Bs和Br/Bs达到最大值,ΔH有最小值.当预烧温度为950 ℃时,Dm最大,Hc最小.综合各方面的性能,最佳的预烧温度确定为800 ℃.     

Structural,Dielectric, and Electrical Properties of BiFeWO6 Ceramic

A polycrystalline sample of BiFeWO₆ was synthesized using a high-temperature solid-state reaction method. The formation of the single-phase compound was checked using an x-ray diffraction technique. The surface morphology recorded by scanning electron microscopy exhibited a uniform distribution of grains of different sizes on the surface of the sample. The existence of ferroelectric properties in the material was confirmed by temperature-dependent dielectric and polarization studies. The temperature and frequency dependence of the electrical properties (impedance, modulus, and conductivity) of the compound were studied using a complex-impedance spectroscopy technique. The frequency dependence of the modulus and impedance plots confirmed the presence of dielectric and conductivity relaxation processes of non-Debye type. The frequency dependence of the alternating-current (ac) conductivity obeys Jonscher’s universal power law.     

Effects of Synthesis Temperature on the Microstructure and Thermoelectric Properties of Te-Se Codoped Skutterudites

Skutterudite compounds Co₄Sb_11.3Te_0.5Se_0.2 were synthesized by solid-state reaction at different temperatures (853 K, 903 K, 953 K, and 1003 K) with subsequent spark plasma sintering. x-Ray diffraction, field-emission scanning electron microscopy, and electron probe microanalysis were utilized to analyze the phase structure, microstructure, and actual compositions of the samples. The results showed that the actual composition and the grain size vary with the synthesis temperature. The thermoelectric properties of all samples were measured in the temperature range of 300 K to 800 K. As the synthesis temperature increases, the electrical conductivity increases rapidly, the absolute Seebeck coefficient falls, and the thermal conductivity first decreases and then increases. The highest dimensionless figure of merit ZT was achieved for the sample synthesized at 953 K, exceeding 1.0 at high temperature.     

钛酸锶钡电介质材料的显微结构和基本性能

钛酸锶钡（BSTO）铁电材料在微波和信息等领域具有很大的优势和潜力，该文综述了该材料的结构和基本介电性能方面的研究情况，并重点讨论了BSTO材料中的晶粒尺寸效应，最后对在电场和频率作用下材料的特殊性能进行了简单介绍。     

BaTiO3烧结陶瓷的微结构及介电性能研究

以超重力反应沉淀法制得的纳米BaTiO3为初始粉体,在不同温度烧结得到BaTiO3陶瓷。分别用SEM和阻抗分析仪测试陶瓷微结构和介电性能。结果表明：陶瓷微结构尤其晶粒尺寸对陶瓷介电性能影响极大;烧结温度低于1250℃时得到细晶粒陶瓷(d=300～400nm),表现出明显的低介电常数和相变弥散的特征;烧结温度达1250℃时得到陶瓷超出细晶粒陶瓷范围,烧结温度为1300℃时,得到陶瓷晶粒尺寸为3～4μm,室温介电性能优于粗晶粒陶瓷。     

热处理温度对Mn－Co－Ni厚膜热敏电阻浆料特性的影响

通过对Ｍｎ－Ｃｏ－Ｎｉ系过渡金属氧化物材料和导电相进行热处理，使Ｍｎ－Ｃｏ－Ｎｉ浆料制作的热敏电阻敏感特性和阻值分散性明显改善。     

热处理温度对Mn－Co－Ni厚膜热敏电阻浆料特性的影响

通过对Ｍｎ－Ｃｏ－Ｎｉ系过渡金属氧化物材料和导电相进行热处理，使Ｍｎ－Ｃｏ－Ｎｉ浆料制作的热敏电阻敏感特性和阻值分散性明显改善。     

Effects of Carbon Coating on Microstructure and Dielectric Properties of CaCu3Ti4O12

CaCu₃Ti₄O₁₂ (CCTO) powders coated with carbon were synthesized by using a high-energy ball milling method. The obtained samples were characterized by x-ray diffraction, transmission electron microscopy and scanning electron microscopy. The carbon-coated CCTO particles had a rough surface, which resulted from the growth of the carbon coating on the CCTO particles. It was found that the CCTO phase was observed as the major phase and no reaction occurred between the carbon and CCTO during the sintering process. The grain size of the CCTO ceramics decreased with the increase in carbon content, which indicated that carbon inhibits grain growth of CCTO ceramics. Specially, the dielectric constant decreased with the increase in carbon content. And CCTO1 ceramic (mass ratio of CCTO: carbon = 10:1) showed a lower dielectric constant (3.74 × 10⁴), with the dielectric loss value (0.04) much lower than that of CCTO at 20°C (10 k Hz).     

Aqueous-Develop,Photosensitive Polynorbornene Dielectric: Optimization of Mechanical and Electrical Properties

The impact of thermal cure conditions on the mechanical and electrical properties of an epoxy cross-linked network incorporating a polynorbornene (PNB) dielectric polymer was studied. The cross-linking of the dielectric composition was achieved by an acid-catalyzed cationic cure reaction initiated by either thermal or photolytic activation of a photoacid generator. It is proposed that the observed mechanical and electrical properties of the fully cured polymer composition are the result of the development of a three-dimensional cross-linked network tying together the PNB polymer and multifunctional epoxy additives. The epoxy ring-opening reaction was measured using Fourier-transform infrared spectroscopy. The reduced modulus, internal film stress, dielectric constant, and swelling behavior of cross-linked films were studied as a function of curing temperature. Trends in the observed properties are explained by formation of a three-dimensional cross-linked network and degradation of the cross-links between the multifunctional epoxy additives at high temperature. It was also found that exposure of the film to aqueous base plays a role in the cure process and has a positive effect on the final properties. The optimum values of modulus, dielectric constant, residual stress, and moisture content were found for films cured at 160°C for 1 h. This relatively low cure temperature is potentially advantageous in device assembly and processing.     

BiYbO3掺杂对KNN LS压电陶瓷微结构与电性能的影响

采用传统陶瓷烧结工艺,制备了BiYbO3掺杂的xBiYbO3-0.95(K05Na0.5)NbO3-0.05LiSbO3(xBY-KNN-LS)(x=0～0.002,摩尔分数)无铅压电陶瓷.研究了BiYbO3掺杂对陶瓷相结构、显微组织和电性能的影响.结果表明,随着BiYbO3掺杂含量的增加,晶粒变细,居里点逐步向低温方向移动,压电性能先增加后降低,介电损耗tan δ先增加后减小.在0≤x≤0.001 5的范围内,存在斜方相与四方相共存的准同型相界,当x=0.1％时得到最佳电性能:压电常数d33=245 pC/N,机电耦合系数kp=44.75％,居里温度Tc =365℃,tan δ=4.5％.     

Sb2O3对钛酸锶钡基陶瓷介电性能及结构的影响

采用传统固相法制备Sb2O3掺杂(Ba0 612Sr0.38Y0.008)TiO3系电容器介质陶瓷,研究了不同质量分数的Sb2O3在各烧结温度下对体系介电性能及微观结构的影响.当Sb2O3的掺杂量为0.4%时,试样在1 320℃下保温2 h,体系的室温相对介电常数可达3 000,介电损耗仅为2×103,居里温度向负温方向移动至-24℃.研究表明:两性氧化物Sb2O3通过占据钙钛矿晶格A位,显著降低了体系相对介电常数及介质损耗,起到了良好的移峰及展宽效应;与此同时,Sb2O3改善了体系微观形貌,有效降低晶粒尺寸.     

铌钴镧掺杂对BaTiO3陶瓷结构与介电性能的影响

根据超薄介质层对高介电常数和细晶结构介质陶瓷材料的需要,采用非均匀形核淀积方法实现Nb、Co、La的氧化物与BaTiO3(BT)水热粉体在纳米水平上的均匀混合。研究了该方法制备的Nb、Co、La掺杂BT陶瓷的相结构、显微结构以及介电性能。实验发现,La、Nb、Co的掺杂可获得致密细晶BT陶瓷,晶粒尺寸可控制在300nm范围内,室温相对介电常数达到3400,介温稳定性符合X7R要求。     

Nb、Co、La掺杂对BaTiO3介质陶瓷性能的影响

为了改善钛酸钡基陶瓷的烧结性能,调控细晶结构,提高工艺稳定性和材料的介电特性,采用铌、钴、镧的柠檬酸-EDTA金属有机盐复合螯合前驱液表面包覆法对水热BaTiO3(BT)粉体进行Nb2O5、CoO、La2O3掺杂改性。实验结果表明:该工艺能够实现改性组分金属有机盐前驱物在BT上的均匀包覆,形成(Ba1–3Lax)(Ti1–Nb2Cox)O3x/2xx/3/3固溶体。当r(Nb/Co)>2时,材料呈铁电弛豫特性;r(Nb/Co)<2时,呈一般铁电特性;当r(Nb/Co)=2,随着La掺量的增加,材料的铁电弛豫特性增加;当r(Nb/Co)>2和r(Nb/Co)<2时,则La的掺量对材料的介电温度特性影响不大。     

Effects of Partial Replacement of Iron with Tungsten on Microstructure,Electrical, Magnetic and Humidity Properties of Copper-Zinc Ferrite Material

This paper presents the analysis of the influence of partial replacement of iron with tungsten on the properties of copper-zinc spinel ferrite material. The samples of Cu_0.5Zn_0.5W _x Fe_2?x O₄ spinel powder ferrites were prepared by using a sol–gel self-combustion technology. The ferrite samples were treated for 30 min at 1000°C. The x-ray diffraction was used in order to establish the differences between the phase compositions of ferrites with different tungsten content. Scanning electron microscopy was used to highlight the influence of the tungsten content on the crystallites. All the samples of Cu_0.5Zn_0.5W _x Fe_2?x O₄ were subject to investigation of the influence of the substitution of tungsten upon their electrical and magnetic properties. The measurements of the electrical properties were performed in different humidity conditions, in order to highlight the effect of moisture conditions on the electrical properties of the material and to analyze the applicability of Cu_0.5Zn_0.5W _x Fe_2?x O₄ ferrite for resistive or capacitive humidity sensors.     

Sol-Gel法制备BST铁电薄膜及其性能分析

用Sol-Gel法制备出表面致密,界面清晰的BST铁电薄膜。分析了BST薄膜的J-V特性,由于使用了不同的上下电极,导致J-V曲线的不对称,且在外延生长的Pt电极上制备的BST薄膜有较低的漏电流。分别在大气和干燥气氛下测量了BST薄膜的介电特性,分析结果表明:湿度对BST薄膜的介电特性有很大的影响,为了得到正确的介电特性,其测量必须在真空或干燥气氛下进行。     

Microstructure and Electrical Properties of Low Temperature Processed Ohmic Contacts to p‐Type GaN

With Ni/Au and Pd/Au metal schemes and low temperature processing, we formed low resistance stable Ohmic contacts to p‐type GaN. Our investigation was preceded by conventional cleaning, followed by treatment in boiling HNO₃:HCl (1:3). Metallization was by thermally evaporating 30 nm Ni/15 nm Au or 25 nm Pd/15 nm Au. After heat treatment in O₂ + N₂ at various temperatures, the contacts were subsequently cooled in liquid nitrogen. Cryogenic cooling following heat treatment at 600 ·C decreased the specific contact resistance from 9.84·10^?4 Ωcm² to 2.65·10^?4 Ωcm² for the Ni/Au contacts, while this increased it from 1.80·10^?4 Ωcm² to 3.34·10^?4 Ωcm² for the Pd/Au contacts. The Ni/Au contacts showed slightly higher specific contact resistance than the Pd/Au contacts, although they were more stable than the Pd contacts. X‐ray photoelectron spectroscopy depth profiling showed the Ni contacts to be NiO followed by Au at the interface for the Ni/Au contacts, whereas the Pd/Au contacts exhibited a Pd:Au solid solution. The contacts quenched in liquid nitrogen following sintering were much more uniform under atomic force microscopy examination and gave a 3 times lower contact resistance with the Ni/Au design. Current‐voltage‐temperature analysis revealed that conduction was predominantly by thermionic field emission.     

基片对SrTiO3薄膜结构与介电性能的影响

对比研究了MgO和LaAlO3(LAO)单晶基片上采用脉冲激光法生长的SrTiO3(STO)薄膜的微观结构和介电性能。通过XRD,AFM和制备叉指电容测量的方法研究发现,在MgO基片上生长高质量(00L)织构STO薄膜需要较高的生长温度;LAO基片上的STO薄膜更加平整;而MgO上的STO薄膜具有更高的零偏压介电常数和更强的非线性介电性质。     

纳米ZnO掺杂对压敏阀片电性能和组织的影响

研究了纳米级ZnO粉料对压敏阀片的压敏电压、漏电流和压比的影响,并对其微观结构进行了分析研究,从理论上探讨了纳米ZnO影响压敏阀片电性能与微观结构的机理。研究结果表明,氧化锌压敏阀片中加入纳米ZnO后,其压敏电压显著提高。在质量分数为0~30%的范围内,随着纳米ZnO含量的增加,压敏阀片的压敏电压明显提高,其压比也呈升高趋势。当纳米ZnO含量为30%时,压敏电压约达547.54 V/mm,压比为1.149。在0~10%的范围内,随着纳米ZnO含量的增加,压敏阀片的漏电流呈下降趋势,而在10%~30%的时,漏电流又随纳米ZnO的含量的增加而升高。当纳米ZnO的含量为10%时,漏电流最小,为0.6 mA。